Electron microscopic localization of the (Na ion plus K ion)-ATPase in brain of the knive-fish has continued in collaboration with Dr. Wood. More recent studies have centered upon the localization in certain astrocytic processes and in sub-lemmal cisternae of axons. In collaboration with Dr. Morest, we are exploring the use of E.M. techniques to establish the "sidedness" of the localization of ATPase antigens in electroplax membranes.